A plasma display panel discharges intense near infrared rays and electromagnetic wave in principle. Since near infrared rays act on neighboring electronic instruments such as a cordless phone and a video cassette recorder using a near infrared remote control, particularly at a wavelength range of 800 to 1050 nm and cause erroneous motion, there is a request for a panel having a function of shielding near infrared rays at 800 to 1050 nm.
With respect to near infrared rays shield, there have been conventionally studied variously those containing metal ions such as copper and iron and those containing near infrared absorbing dyes such as a nitroso compound and its metal complex salt, a cyanine compound, a squalilium compound, a dithiol metal complex compound, an aminothiophenol metal complex compound, a phthalocyanine compound, a naphthalocyanine compound, a triarylmethane compound, an immonium compound, a diimonium compound, a naphthoquinone compound, an anthraquinone compound, an amino compound and an aminium salt compound.
As its use mode, there can be considered (a) a transparent polymer film prepared by kneading a near infrared absorbing dye with a resin, (b) a polymer film prepared by a casting process by dispersing and dissolving the near infrared absorbing dye in a concentrated solution of a resin or a resin monomer/organic solvent, (c) those prepared by adding the dye to a resin binder and an organic dye solvent and coating the solution on a transparent polymer film, (d) those obtained by containing the near infrared absorbing dye in a pressure-sensitive adhesive, etc.
It is impossible that the above-mentioned near infrared absorbing dye covers the above-mentioned range of 800 to 1050 nm by only one dye. Usually, a plurality kinds of dyes, specifically, a dye absorbing near infrared rays with comparatively short wavelength and a dye absorbing near infrared rays with comparatively long wavelength among near infrared rays are used in combination.
Hereat, products are generally prepared by pasting a plural number of layers by the above-mentioned methods (a) to (c). However, considering labor hour at production, cost, and light transmittance, it is status quo that the much more the layers are laminated, the higher the cost is and the lower the light transmittance is. It is a direction for further reducing cost and improving the light transmittance that the number of layers is reduced.
Consequently, it is considered that if a dye is compounded in a pressure-sensitive adhesive used for interlayer adhesion by the method (d), the number of layers of plastic films used is reduced, cost is reduced and light transmittance is improved. This method has been studied hitherto and there is known a front filter for plasma display using a pressure-sensitive adhesive in which visible light absorbing dyes such as a methine dye and a tetraazaporphyrin dye are compounded (for example, Patent Documents 1 to 3).
Further, it is proposed that a diimmonium dye being a conventional near infrared absorbing dye that is preferably used for a front filter for plasma display, or a nickel dithiol dye known in Patent Document 4 is also compounded in a pressure-sensitive adhesive (Patent Documents 4 to 6).
Patent Document 1: Japanese Unexamined Patent Publication No. 2004-107566
Patent Document 2: Japanese Unexamined Patent Publication No. 2002-40233
Patent Document 3: Japanese Unexamined Patent Publication No. 2002-4372619
Patent Document 4: Japanese Unexamined Patent Publication No. 9-230134
Patent Document 5: Japanese Unexamined Patent Publication No. 10-156991
Patent Document 6: Japanese Unexamined Patent Publication No. 2001-207142